An example of an expansion device for expanding a pipe is disclosed in International patent application publication No. 02/086 285. This publication discloses an expansion device having a front end and a rear end and it comprises an expansion cone tapering in forward direction towards the front end of the expansion device, a set of guide rods, an actuator capable of displacing, during normal operation, the expansion cone and the set of guide rods relative to each other, and two one-directional end anchors arranged at either end of the set of guide rods, which end anchors are capable of cooperating with the inner surface of the pipe to prevent movement of the set of guide rods relative to the pipe, when during normal operation, the expansion cone is displaced relative to the guide rods in the forward direction.
The known expansion device is, during normal operation, attached to the lower end of a tubular.
Normal operation of known expansion devices comprises two steps, an expansion step and a reset step. The initial position of the expansion step is that the end anchors are set, wherein the end anchor at the front is set in the unexpanded part of the pipe and anchor at the back is set in the part of the pipe that has been expanded, and wherein the expansion cone is in a first position close to the end anchor. The actuator is powered so as to force the expansion cone in forward direction to expand the pipe, during expansion the end anchors take up the axial force. The actuator is powered by fluid under pressure supplied through the tubular to which the expansion device is attached. When the anchor has arrived at the front anchor, powering the actuator is interrupted and the displacement of the expansion cone stops.
Resetting the expansion cone is done by pushing the tubular in order to move the expansion device forwards. The end anchors do not prevent this displacement, because they work in one direction only. The expansion cone cannot move forwards, so that the guide rods are displaced forwards relative to the expansion cone. When the end anchor at the back has arrived at the expansion cone, the displacement of the guide rods is interrupted and the expansion device has returned to its initial state. At the start of expanding a pipe, the front anchor can be set in the unexpanded pipe section, whilst the back anchor has no expanded pipe in which it can set. On completing the expansion, the back anchor can be set in the expanded pipe section, whilst the front anchor extends out of the pipe.